Method for optimising the production technology of rolled products

ABSTRACT

The inventive method is used for optimising a hot and/or cold strip mill process. Said method consists in discreetly measuring the technological parameters of a strip milling and the angular rates of the working rollers of mill stands and table rollers, in defining the liner speed of the strip and selecting a specified number of strip sections having an equal length and used for a subsequent averaging of at least three values of technological parameters for each section, in determining the normative part of the length of the strip, which is divided into sections, for a specific range of rolled products, defining useful quality for each section with respect to the averaged values of the technological parameters of the section rolling, comparing the useful quality with prescribed limits, determining the part of the strip length for which the useful quality values lie within prescribed limits and in using said technological parameters as a standard for milling a strip of the same range or for the range close thereto if the thus obtained part of the strip length is equal to or higher than the normative part, or for rectifying the technological parameters if the thus obtained part is lower than the normative part.

FIELD OF THE INVENTION

The invention relates to the art of mechanical treatment of metal bypressure, i.e. to production of rolled products, in particular itrelates to controlling of rolling mills and handling of the producedarticles in the course of their treatment, and more particularly itrelates to the rolling mill's monitoring and adjusting devices that areoperable to respond to different variables of the rolled sheets. To acertain extent, the invention relates to auxiliary operations fortreatment of metal in the course of rolling thereof.

The invention is particularly intended for optimizing the process of hotand/or cold rolling of strips.

BACKGROUND OF THE INVENTION

Known is the method for adjusting the rolling process, comprising thesteps of measuring thickness of a rolled strip, and carrying out thecorrecting actions as to actuators of the roll drives when a rolledstrip thickness deviates from predetermined values (patent RU No.2125495, assigned to SMS Schloemann-Siemag AG, IPC B 21 B 37/00, 1999).This method provides for measurement of only one parameter, and does notprovide for taking into account a change in speed of a rolled strip.

Known is the method for adjusting the rolling process, comprising thesteps of measuring the strip rolling process parameters by measuringinstruments at a number of points along a mill, and outputtingappropriate correcting actions as to actuators (patent RU No. 2078626,assigned to Siemens AG, IPC B 21 B 37/00, 1997). Said method does notinclude the step of tracking the relationship between the monitoredprocess parameters and particular length values of a rolled strip. Forthat reason, any exact moment for applying the correcting actions cannotbe determined while selecting said correcting actions.

Also known is the method of adjustment of the rolling process,comprising the steps of discretely measuring the monitored strip rollingprocess parameters at a number of points along a mill, measuring angularvelocities of the stand working rolls and table rolls, basing on whichmeasurements a strip linear speed is determined; defining, according tothe obtained data, a certain number of equally sized strip sections forsubsequent averaging of at least three values of the measured monitoredvariables at each given section, and determining the required correctingactions as to actuators on the basis of the averaged values of themonitored parameters for a given section (patent RU No. 2177847, cl. B21 B 37/00, 2002). In the applicant's opinion, this method is the artthat is the most pertinent to the claimed invention.

SUMMARY OF THE INVENTION

The invention is based on the concept of continuous, more exactly:quasi-continuous measurement of such process parameters as, forinstance, consumer properties of a rolled strip along its length in thecourse of rolling. These properties can be as follows: ultimate strength(σ_(us)) yield strength (σ^(y)), and/or elongation (δ) of a rolledstrip, etc.

According to the invention: the monitored parameters are measured when astrips moves under an appropriate sensor, and/or at an appropriatemeasuring arrangement; further, for excluding a possibility that themeasurement results would be affected by any occasional fluctuations ofmeasured quantities, which are inevitable under conditions of hightemperatures and large masses of a moving metal, at least three valuesobtained at adjacent measurement points are averaged, the obtainedaveraged values of the process parameters of a rolled article arecompared with the standard values, and when said quantities do notcoincide, the correcting actions are effected at the relevant sectionsof a mill. Such action may consist in modifying the gap between rolls,or the cooling action.

More particularly, according to the invention, implemented is a methodfor optimizing the rolling process by way of determination of settingsfor a mill, provision of sensors and measuring arrangements at a mill(for example, for selecting specimens of a rolled material) to determineparameters of a rolled strip while a strip is moving, to read andautomatically process the sensor indications or the sampling results,and for determining the controlling actions to be performed as to therolling process. Further, the rolling process parameters that should bemonitored according to production specification of a given rolledproducts' batch are preset. The invention also provides for systematicmeasuring of the preset parameters' quantities in the course of movementof a rolled strip over a rolling mill. In this context, the “systematic”term means as frequent measurements of parameters as the usedinstruments allow such frequency, or as required by the monitoringconditions. Then, a number or length of sections of a rolled strip aredefined; for each one of the sections, values of the rolling parameters'measured quantities should be obtained separately. Under conditions ofthe Examples described below, number of sections of the 800-meter (atexit) strip was 50 sections, so that, accordingly, one section was 16 mlong. After that, the measured quantities relating to a given section ofa rolled strip are averaged, the averaged quantities of the measuredparameters are compared with the quantities defined in conformity withproduction specifications of a given batch of rolled articles. When thecompared quantities do not coincide to an extent beyond certaintolerances, then the mill settings are corrected for rolling of nextstrip, in respect of which next strip these steps are repeated. When thecomparison result is positive, the existing settings remain for rollingof next strip.

More specifically, the invention further comprises the steps of:discrete measuring of the strip rolling process parameters, measuring ofthe angular velocities of the stand working rolls and tables rolls,determining the strip linear speeds; defining a certain number ofequally sized strip sections for subsequent averaging of at least threevalues of the measured process parameters at each given section, settinga rated portion of the strip length subdivided into sections; for agiven rolled products range, further defining the consumer properties ateach one of the rolled strip sections depending on the averaged valuesof each section's measured process parameters; comparing the definedconsumer properties with the preset limits of the consumer properties;defining a strip length portion wherein the consumer properties arewithin the preset limits, and establishing these process parameters asthe primary standard for rolling of strips of the same or proximateproduct range—when this defined strip length portion is not less thanthe rated portion, or amending the process parameters on a newstrip—when said defined strip length portion is less than the rated one.

DETAILED DESCRIPTION OF THE INVENTION EXAMPLE 1

The method was carried out at a continuous wide-strip hot mill. Strips800 m long, made of steel 08nc (semi-killed steel), 4 mm thick, wererolled. Chemical composition of the rolled steel was indicated in theheat log issued by the steel-making unit: Table 1. TABLE 1 Element C SiMn S P Al Content, % 0.09 0.01 0.42 0.023 0.015 0.044

The monitored process parameters were the rolling terminationtemperature (T_(re)) and coiling temperature (T_(co)). For measuring thestrip rolling termination temperature, a pyrometer positioned at exitfrom the last finishing stand in the start of the run-out table wasused; and the coiling temperature was measured by a pyrometer positionedupstream of the coiler. The strip temperature downstream of the finalroughing stand (the sixth stand, T₆) was measured by a pyrometerpositioned in the start of the span between the roughing and finishinggroups of the mill stands. Strip thickness was measured by an X-raythickness gauge at exit from the mill finishing group; strip parameterswere measured discretely 10 times/s by pyrometers and thickness gauge.Angular velocities of working rolls of the final finishing stand, finalroughing stand, of the run-out table and intermediary tables' rolls weremeasured by tachometers mounted on the respective drives. Basing on theangular velocity measurements, taking into account diameters of thestands and table rolls, the strip linear speed was measured, which speedhad the following values: 2 m/s within the span between the roughing andfinishing groups, and 6.5-11.2 m/s downstream of the stands' finishinggroup. For each one of 50 sections 16 m long, basing on a value of thestrip linear speed: a set of the measured values relating to the time,when each one of said strip sections has passed under a relevant sensor,was determined. The number of sections selected in this case wasdetermined, on the one hand, by the response speed of the used measuringsystems and actuators and, on the hand, by the required adjustmentaccuracy. The measured discrete values of instrument indications wereaveraged for each section. As the averaged values were within thetolerances of the rolled products range, next strips were rolled underthe same settings.

EXAMPLE 2

Under the same initial conditions as were used in Example 1, part fromthe process parameters mentioned in said Example: values of σ (ultimatestrength) and δ (elongation) were determined for each one of the stripsections to check them upon their compliance with requirements of theapplicable standards (the general standards and those demanded by acustomer).

The obtained data are summarized in Table 2. TABLE 2 Thickness, σ_(us)Section No. T₆ ° C. T_(rt) ° C. T_(co) ° C. mm MPa δ, %  1 1097 888 5633.04 386.7 30.1  2 1095 900 561 2.84 381.6 29.8  3 1088 900 566 2.80380.7 29.7  4 1081 895 575 2.83 381.5 29.9  5 1073 895 577 2.85 381.129.9  6 1064 889 578 2.88 383.7 30.0  7 1061 883 578 2.93 386.5 30.0  81064 885 583 2.96 384.7 30.1  9 1069 888 583 2.95 383.3 30.1 10 1075 890582 2.94 382.6 30.1 11 1078 894 579 2.91 381.2 30.0 12 1080 896 577 2.89380.7 30.0 13 1081 896 577 2.87 380.7 29.9 14 1080 898 578 2.86 379.629.9 15 1079 896 579 2.86 380.3 30.0 16 1078 898 586 2.86 378.2 30.0 171077 899 584 2.86 378.1 30.0 18 1077 898 582 2.87 378.9 30.0 19 1077 899580 2.86 378.8 30.0 20 1078 902 580 2.85 377.4 29.9 21 1078 903 581 2.84376.8 29.9 22 1077 903 583 2.84 376.4 30.0 23 1074 901 582 2.85 377.530.0 24 1070 899 582 2.86 378.4 30.0 25 1068 897 582 2.86 379.3 30.0 261068 897 581 2.87 379.5 30.0 27 1070 899 580 2.86 378.8 30.0 28 1074 900581 2.85 378.1 30.0 29 1077 904 583 2.84 376.0 30.0 30 1080 906 584 2.83374.9 30.0 31 1082 906 585 2.82 374.7 29.9 32 1082 906 587 2.82 374.330.0 33 1082 902 586 2.82 376.4 30.0 34 1079 903 582 2.82 376.6 29.9 351077 901 586 2.82 377.0 29.9 36 1078 901 586 2.82 376.8 30.0 37 1078 900580 2.83 378.3 29.9 38 979 901 585 2.83 377.0 30.0 39 1080 903 590 2.83375.2 30.0 40 1082 904 590 2.83 374.8 30.0 41 1083 905 589 2.82 374.530.0 42 1084 905 590 2.82 374.3 30.0 43 1084 901 590 2.82 376.1 30.0 441082 903 590 2.82 375.2 30.0 45 1080 901 589 2.83 376.3 30.0 46 1078 900599 2.84 375.1 30.1 47 1076 902 602 2.84 373.6 30.1 48 1077 903 601 2.83373.3 30.1 49 1081 904 603 2.81 372.5 30.1 50 1081 898 644 2.88 368.330.6 Tolerance, 1060-1100 880-910 560-590 2.8-3.2 295.4-384.5 >28.5(95%) (95%) (90%) (92%) (92%) (92%) Within 100% 100% 90% 100% 94.0% 100%Tolerance, Fitness to yes yes yes yes yes yes use

It follows from Table 2 that the strip length portion wherein theconsumer properties' values are within the preset limits, exceeds thestrip length rated portion having the consumer properties' values withinthe preset limits (every rolled product range is rated by theengineering specifications on the basis of previous investigations),i.e. for a given chemical composition of steel, the rolling terminationtemperature of 886° C. and that of coiling of 680° C. provided the stripmechanical properties required by the applicable standard. These valueswere subsequently used as the primary standard for strip rolling of thesame or proximate range of rolled products (having a proximate metalcomposition and thickness). For subsequent rolling of strips of the sameor proximate product range, the established primary standard was usedfor setting T_(rt) and T_(ro) process values.

EXAMPLE 3

Under the initial conditions of Example 2, strips selected from a grouphaving a somewhat different chemical composition were rolled. Data onthe same measurements for this strip are summarized in Table 3. TABLE 3Thickness, σ_(us) Section No. T₆ ° C. T_(rt) ° C. T_(co) ° C. mm MPa δ,%  1 1082 905 583 2.99 375.5 30.2  2 1076 908 580 2.91 374.6 32.9  31070 903 579 2.86 377.1 32.8  4 1068 901 572 2.83 379.2 32.7  5 1068 900568 2.80 380.4 32.7  6 1069 897 564 2.78 382.4 32.6  7 1071 897 552 2.77382.8 32.6  8 1072 899 560 2.76 382.2 32.5  9 1074 897 558 2.78 383.432.5 10 1074 898 560 2.79 382.6 32.6 11 1074 899 562 2.80 381.8 32.6 121074 898 565 2.82 381.8 32.7 13 1074 895 567 2.83 382.8 32.7 14 1072 893567 2.85 383.7 32.7 15 1072 892 569 2.86 383.9 32.7 16 1073 893 568 2.87383.6 32.8 17 1075 894 568 2.86 383.1 32.7 18 1075 895 567 2.87 382.832.7 19 1076 896 567 2.86 382.4 32.7 20 1076 895 566 2.87 383.0 32.7 211075 897 566 2.86 382.1 32.7 22 1075 895 565 2.86 383.2 32.7 23 1073 893564 2.86 384.3 32.7 24 1068 891 563 2.87 385.4 32.7 25 1065 887 563 2.88387.2 32.7 26 1066 884 563 2.89 388.6 32.7 27 1068 888 566 2.90 386.232.8 28 1071 889 565 2.90 385.9 32.8 29 1072 893 566 2.88 383.9 32.8 301073 895 568 2.88 382.7 32.8 31 1073 893 566 2.87 383.9 32.7 32 1071 892564 2.86 384.7 32.7 33 1068 890 564 2.87 385.6 32.7 34 1066 887 566 2.87386.7 32.7 35 1067 886 571 2.88 386.3 32.8 36 1068 889 572 2.88 384.732.8 37 1068 889 576 2.89 384.0 32.9 38 1069 890 579 2.90 383.1 32.9 391068 891 574 2.90 383.5 32.9 40 1067 891 571 2.89 384.0 32.8 41 1064 889568 2.89 385.4 32.8 42 1060 885 568 2.90 387.3 32.8 43 1057 884 566 2.90388.1 32.8 44 1058 883 566 2.91 388.5 32.8 45 1065 888 570 2.90 385.532.8 46 1074 893 571 2.89 383.1 32.8 47 1085 901 568 2.87 379.9 32.8 481094 904 567 2.85 378.7 32.7 49 1100 903 620 2.83 370.1 33.2 50 1100 903639 2.89 366.8 33.1 Tolerance, 1060-1100 880-910 560-590 2.8-3.2294.4-384.5 >28.5 (95%) (95%) (90%) (92%) (92%) (92%) Within 96.0% 100%94.0% 100% 68.0% 100% Tolerance, Fitness yes yes yes yes no yes to use

Table 3 shows that values of σ_(us) (ultimate strength) exceed thestandard values by 32% of the strip length, while the allowed excessivevalue is 8%. For this reason, for rolling of next strip of that group,the correcting action to be effected at its relevant sections wasmodified, and said measurement procedure was entirely repeated so thatthe needed fitness of the strip's rated portion was provided; then thedefined mode was being maintained in the course of rolling of otherhomogeneous blanks.

INDUSTRIAL APPLICABILITY

The invention can be suitably used first of all for rolling of groups ofhomogeneous blanks, and also can be used for rolling of single blanks,particularly in the cases when subsequent use of separate portions of arolled sheet for different purposes or different subsequent processes isanticipated.

1. A method for optimizing the production technology of rolled products,said optimizing being effected by determination of operation settings ofa rolling mill, comprising the steps of: at the rolling mill,positioning sensors and/or measuring arrangements to determine thevariables of a rolled strip when said strip moves; reading andcomputer-aided processing of indications of said sensors and measuringarrangements, and working-out the controlling actions to which therolling process is to be subjected; said method being characterized inthat it further includes the following steps: presetting the rollingprocess parameters needed to be monitored according to productionspecifications for a given batch of rolled products; systematicmeasuring of values of the preset parameters when a rolled strips movesalong the rolling mill; presetting a number and/or length of the rolledstrip sections, for each of which sections the measured quantities'values of the rolling parameters must be obtained separately; averagingthe measured quantities that relate to a given section of the rolledstrip; comparing the averaged quantities of the measured parameters withthe quantities determined by the production specifications for a givenbatch of rolled products; correcting the rolling mill's settings forrolling of next strip—when the averaged quantities of the measuredparameters do not coincide with the quantities defined by the productionspecifications for a given batch of rolled products; and maintainingsaid quantities for rolling of next strip—when said quantities coincide.2. The method as claimed in claim 1, characterized in that the monitoredparameter is the rolling termination temperature (T_(rt)) or coilingtemperature (T_(co)) of a rolled strip, or a combination thereof.
 3. Themethod as claimed in claims 1 or 2, characterized in that it furtherincludes the following steps: discrete measuring of the strip rollingprocess parameters, measuring the angular velocities of the standworking rolls and table rolls, determining the linear speed of stripmovement, and determining a certain number of the equal-length stripsections for subsequent averaging of at least three values of themeasured process parameters at each one of the sections, furtherestablishing a rated portion of the strip length, subdivided intosections, for a particular range of rolled products; further determiningthe consumer properties at each rolled strip section depending on theaveraged values of the measured process parameters of each sectionrolling; comparing the determined consumer properties with the presetlimits of consumer properties; determining a portion of a strip lengthwherein the consumer properties' values are within the preset limits;and establishing these process parameters as the primary standard forthe same or proximate products range—when said determined strip lengthportion is not less than the rated portion, or amending the processparameters on a new strip—when said determined strip length portion isless than the rated one.